JP2015511186A - Method for producing composite polymer - Google Patents

Abstract

Extrudates containing 10-50% by weight wood pulp fibers and 45-85% by weight thermoplastic polymer are extruded with a die, the extrudate is cut into pellets, the temperature is lower than the extrudate A method for producing a pellet comprising wood pulp fibers and a thermoplastic polymer, comprising removing the pellet from the extrudate using water and filtering the pellet from the water. In one embodiment, the wood pulp fibers in the pellets have a moisture content of 1% or less. In one embodiment, the wood fibers are not swollen. [Selection] Figure 10

Description

CROSS-REFERENCE This application priority application is February 2012 "method of manufacturing a composite polymer (PROCESS FOR MAKING COMPOSITE POLYMER)" filed in 14 days with that of the title U.S. Provisional Patent Application No. 61 / 598,876 Have the right to claim and claim its benefit, the contents of which are incorporated herein by reference.

FIELD OF THE INVENTION This invention relates to polymer composites derived by melt processing a polymer matrix with chemical wood pulp fibers.

FIG. 1 is a schematic illustration of particles used in the production of a polymer composite. FIG. 2 is a schematic representation of the particles used in the production of the polymer composite. FIG. 3 is a schematic representation of the particles used in the production of the polymer composite material. FIG. 4 is a schematic representation of the particles used in the production of the polymer composite material. FIG. 5 is a schematic representation of the particles used in the production of the polymer composite. FIG. 6 is a schematic diagram of a mixer. FIG. 7 is a schematic diagram of a pellet mill. FIG. 8 is a schematic diagram of a pellet mill. FIG. 9 is a schematic representation of a single screw extruder useful for producing the pellets of the present invention. FIG. 10 is a schematic illustration of an embodiment of an apparatus and method for producing a polymer composite having a chemical wood pulp fiber content of 50% by weight or less. FIG. 11 is a cross-sectional view of the open surface of the first twin screw mixer. FIG. 12 is a side view of a restrictor for the first twin screw mixer. FIG. 13 is a front view of a restrictor for the first twin screw mixer. FIG. 14 is a schematic representation of another embodiment of an apparatus and method for producing a polymeric composite material having a chemical wood pulp fiber content of 50% by weight or less. FIG. 15 is a schematic diagram of an underwater pelletization system.

  The present invention is directed to providing an economic means of producing composite polymeric materials comprising wood pulp fibers and thermoplastic polymers. In one embodiment, the wood pulp fiber is a chemical wood pulp fiber. In one embodiment, the wood pulp fibers are kraft chemical wood pulp fibers. In one embodiment, the wood pulp fibers are bleached wood pulp fibers. In one embodiment, the wood pulp fibers are bleached chemical wood pulp fibers. For simplicity, the term “wood pulp fiber” is used, but it should be noted that bleached chemical wood pulp fiber has properties not found in some other fibers.

  The present invention can utilize a number of tree species as pulp fiber sources. Coniferous and hardwood species and mixtures thereof can be used. They are also known as soft and hard materials. Typical softwood varieties include various spruce (eg, Sitka Spruce), fir (Douglas fir), various tsutsu (American eel), American larch, larch, various pine (Southern pine, strobe pine, And Caribbean pine), cypress and American cedar or mixtures thereof. Typical hardwood varieties are avian cat, aspen, cotton willow, linden, birch, beech, linden, rubber, elm, eucalyptus, maple oak, poplar, and sycamore or mixtures thereof.

  Whether to use soft or hard grades can be determined in part by the desired fiber length. Hardwood or hardwood species have a fiber length of 1-2 mm. Softwood or softwood species have a fiber length of 3.5-7 mm. Douglas fir, American fir, American hemlock, western larch, and southern pine have fiber lengths in the 4-6 mm range. Pulping and bleaching and dicing can cause the fibers to break and reduce the average length.

  Cellulose wood pulp fibers differ from wood fibers in that lignin is removed and a portion of hemicellulose is removed. In wood fibers, these materials remain retained. The amount of material remaining in the wood pulp fibers is expected to depend on the production process.

  In mechanical pulp, the fibers are separated by mechanical means such as grinding, for example, but this process may involve steaming and some chemical pretreatment with sodium sulfite. As lignin softens, the fibers fall apart. Lignin and hemicellulose, as well as much of the cellulose, remains in the fiber. The yield, ie the percentage of material remaining after pulping, is high. Although the fiber can be bleached with peroxide, much of the material is not removed in this process.

  In chemical pulping, lignin is removed during the chemical reaction between the wood chips and the chemical for pulping. Hemicellulose may also be removed during this reaction. The amount of material removed is expected to depend on the chemicals used in the pulping process. The amount of material removed by the kraft or sulfate process is less than the sulfite or kraft process in the prehydrolysis stage. The yield in the kraft process is higher than the yield in the sulfite process or kraft by prehydrolysis. The latter two processes produce a product that contains a high percentage of cellulose and little hemicellulose or lignin.

Bleached chemical wood pulp has more lignin and hemicellulose removed.
In pulp production, woody material is disintegrated into fibers during the chemical pulping process. The fiber may then optionally be bleached. The fibers and water are then combined in a stock chest to form a slurry. The slurry is then passed through a head box, placed on a wire, dewatered and dried to form a pulp sheet. Additives may be combined with the fibers in the stock chest, in the headbox, or both. The material may be sprayed onto the pulp sheet before, during or after dehydration and drying. The kraft pulping process is typically used for the production of wood pulp.

  There is a difference between wood fiber and wood pulp fiber. Wood fibers are a group of wood fibers joined by lignin. The wood pulp fiber lumen collapses during the drying process. The dried chemical wood pulp fibers are flat. The lumens of each wood fiber in the wood fiber bundle remain open. Flat wood pulp fibers are more flexible than wood fibers.

  Cellulosic wood pulp fibers may be in the form of commercially available cellulosic wood pulp. Pulp is typically sent in roll or packaged form. The pulp sheet has two opposing substantially parallel faces, the distance between these faces being the thickness of the particles. A typical pulp sheet may be 0.1 mm to 4 mm thick. In some embodiments, the thickness may be between 0.5 mm and 4 mm.

The wood pulp sheet is formed into particles to facilitate metering and mixing with the thermoplastic polymer.
Fiber sheet and particles ^may have a basis weight of 12g / m 2 (gsm) ~2000g / m 2. In one embodiment, the particles ^may have a basis weight of ^{600g / m 2 ~1900g / m 2} . In another embodiment, the particles ^may have a basis weight of ^{500g / m 2 ~900g / m 2} . For paper sheets, one embodiment may have a basis weight of 70 gsm to 120 gsm. In other embodiments, the paperboard may have a basis weight of 100 gsm to 350 gsm. In other embodiments, the special purpose fiber sheet may have a basis weight of 350 gsm to 500 gsm.

  The characteristics of the particles can also change with pulp additives or pretreatment. Debonder treated pulp is expected to provide looser particles than undebonded pulp. Loose particles can be more easily dispersed in the material combined with the particles. Pulp sheet thickness is one of the factors that can determine particle thickness.

In one embodiment, the particles are hexagonal, one embodiment of which is shown in FIG. The hexagons may be of any type, from completely equilateral hexagons to completely asymmetric hexagons. If they are not equilateral, the major axis may be 4-8 millimeters (mm) and the minor axis may be 2-5 mm. Some of the hexagonal sides may have the same length, and some or all of the sides may have different lengths. The circumference or outer circumference of the hexagon may be 12 to 30 mm, and the area of the upper or lower surface 24 or 26 of the particles may be 12 to 32 mm ² . In one embodiment, the particles have a thickness of 0.1 to 1.5 mm, a length of 4.5 to 6.5 mm, a width of 3 to 4 mm, and an area of one face of 15 to 20 mm ^2. It may be. In other embodiments, the particles may have a thickness of 1 to 4 mm, a length of 5 to 8 mm, a width of 2.5 to 5 mm, and a surface area of 12 to ²⁰ mm ² .

Two examples of particles shaped into hexagons are shown.
1-3, the particle 10 is hexagonal and has two opposing sides 12 and 18 that are equal in length and longer than the other four sides 14, 16, 20, and 22. The other four sides 14, 16, 20, and 22 may be the same length as shown, or the four sides may be different lengths. Two of these sides, for example, 14 and 20 or sides at both ends such as 14 and 22 may be the same length, or the other two sides at both ends, 16 and 22 or 16 and 20 , May be the same length or may have different lengths. In each of these variations, sides 10 and 18 may be the same length or different lengths. The ends of the particles may be sharp or rounded.

The distance between the upper part 24 and the lower part 26 of the particle 10 may be 0.1 mm to 4 mm.
4 and 5 illustrate embodiments in which the length of each of the six sides of the hexagon is different. The illustrated embodiment is exemplary. The order of the side lengths and the size of the side lengths may vary.

Particles having the shapes, sizes, and basis weights described above can be weighed by weight reduction or metered delivery systems well known in the art.
The alignment of the fibers within the particles may be parallel to the major axis of the hexagon, or perpendicular to the major axis of the hexagon, or in any direction therebetween.

Hexagonal particles can be formed with a Henion dicer, but other means can be used to produce hexagonal particles.
Other forms of pulp particles can also be used. The ease of addition may depend on the shape of the particles.

  The polymer matrix functions as a host polymer, which is a component of a melt processable composition that includes a chemical wood pulp feed. Melt processing can be used to combine the polymer and chemical wood pulp fibers. In melt processing, the polymer is heated and melted to combine the polymer with chemical wood pulp fibers. During this process, the fibers are singulated.

The polymer is thermoplastic.
A wide variety of polymers conventionally recognized in the art as suitable for melt processing are useful as the polymer matrix. The polymer matrix substantially includes polymers that may be said to be difficult to melt process, particularly when combined with interfering elements or other immiscible polymers. These include both hydrocarbon and non-hydrocarbon polymers. Examples of useful polymer matrices include, but are not limited to, high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), polypropylene (PP), polyolefin copolymers (eg, ethylene -Butene, ethylene-octene, ethylene vinyl alcohol), polystyrene, polystyrene copolymers (eg high impact polystyrene, acrylonitrile butadiene styrene copolymers), polyacrylates, polymethacrylates, polyesters, polyvinyl chloride (PVC), fluoropolymers, liquid crystal polymers , Polyamide, polyetherimide, polyphenylene sulfide, polysulfone, polyacetal, polycarbonate, polyphenylene oxide, polyurethane, heat Plastic elastomer, epoxy, alkyd, melamine, phenolic resin, urea, vinyl esters or combinations thereof and the like. In certain embodiments, the most preferred polymer matrix is a polyolefin.

  Polymer matrices derived from recycled plastics are also applicable because they are often less expensive. However, since such materials are often derived from materials derived from multiple types of waste streams, they can have very different melt rheology. This can result in materials that are extremely problematic to process. Addition of cellulosic feedstock to the recycled polymer matrix is expected to increase melt viscosity and reduce overall variability, thus improving processability.

  In some embodiments, the following thermoplastic polymers; biopolymers such as polylactic acid (PLA), cellulose acetate, cellulose propionate, cellulose butyrate, etc .; polycarbonates, polyethylene terephthalate, polyolefins such as polyethylene, high density polyethylene, low Density polyethylene, linear low density polyethylene, polypropylene, polystyrene, polystyrene copolymers such as acrylonitrile-butadiene-styrene copolymer (ABS), styrene block copolymer, vinyl chloride (PVC), and recycled plastics may be used .

  Thermoplastic polymers are biopolymer, polylactic acid, cellulose acetate, cellulose propionate, cellulose butyrate, polycarbonate, polyethylene terephthalate, polyolefin, polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polystyrene, polystyrene It can be selected from the group consisting of copolymers, acrylonitrile-butadiene-styrene copolymers, styrene block copolymers, vinyl chloride, and recycled plastics.

  In one embodiment, the chemical wood pulp feed is melt processed with an incompatible polymer matrix (eg, polyolefin). In other embodiments, the chemical wood pulp feed is melt processed with a compatible polymer matrix (eg, a modified cellulosic polymer). For example, when the chemical wood pulp feed of the present invention is melt processed with cellulose propionate (Tenite ™ 350E), the resulting composite material has excellent fiber dispersion and mechanical properties. It was found to have

  The present invention also contemplates the use of compatibilizing materials in the composite formulation. Compatibilizing materials are typically used to improve the wetting of the filler / polymer matrix interface. The addition of a coupling agent or compatibilizer often improves the mechanical properties of the resulting composite. The present invention utilizes compatibilizing materials to improve wetting between the chemical wood pulp fibers of the present invention and the polymeric matrix, as is known in the art. However, the inventors have further found that the addition of a compatibilizing material improves the dispersion between the chemical wood pulp feed of the present invention and certain polymers. Even if the compatibilizing material and the coupling agent act differently to provide compatibility between the two materials, they may be used interchangeably.

  A preferred compatibilizing material for use with polyolefins is a polyolefin-graft-maleic anhydride copolymer. In one embodiment, the polymer matrix and cellulosic feed are melt processed with a polyolefin-graft-maleic anhydride copolymer. Commercially compatible compatibilizers of the present invention include Polybond ™ (Chemtura), Exxelor ™ (Exxon Mobil), Fusabond ™ ( It is sold under the trade names DuPont, Lotader ™ (Arkema), Bondyram ™ (Maroon), and Integrate (Equistar). Are listed. The polymer matrix may contain one or more fillers in addition to the chemical wood pulp feed. The polyolefin in the graft copolymer is expected to be the same as the polyolefin used as the polymer in the polymer matrix. For example, polyethylene-graft-maleic anhydride is expected to be used with polyethylene, and polypropylene-graft-maleic anhydride is expected to be used with polypropylene.

In one embodiment, the compatibilizing material in an amount of about 5-10%, and in another embodiment 0.2-5%, is incorporated into the composite formulation and melt processable composition.
Fillers and fibers other than chemical wood pulp fibers may be added to the fiber / polymer blend to impart desirable physical properties or to reduce the amount of polymer required for a given application. Fillers often contain moisture, thus reducing the effectiveness of the compatibilizer present in the polymer matrix. Non-limiting examples of fillers and fibers include wood flour, natural fibers other than chemical wood pulp fibers, glass fibers, calcium carbonate, talc, silica, clay, magnesium hydroxide, and aluminum trihydroxide. It is done.

  In other forms of the invention, the melt processable composition may contain other additives. Non-limiting examples of conventional additives include antioxidants, light stabilizers, fibers, foaming agents, foaming additives, anti-blocking agents, thermal stabilizers, impact modifiers, biocides, flame retardants, plastics Agents, tackifiers, colorants, processing aids, lubricants, compatibilizers, and pigments. The additive may be incorporated into the melt processable composition in the form of powder, pellets, granules, or in any other extrudable or compoundable form. The amount and type of conventional additives in the melt processable composition can vary depending on the desired physical properties of the polymer matrix and the finished composition. One skilled in the melt processing art can select the appropriate amount and type of additives to suit the particular polymer matrix in order to achieve the desired physical properties of the finished material.

  The composite polymer of the present invention has wood pulp fibers uniformly dispersed in a thermoplastic polymer matrix. First, wood pulp fibers are dispersed in a thermoplastic polymer matrix, where wood pulp fibers are 65 to 90% by weight of the total composition.

  There are problems associated with uniformly dispersing chemical wood pulp fibers throughout the polymer matrix. The fiber is initially in the form of a dry pulp sheet. Drying breaks the pulp fibers. Further, the pulp fibers are bonded by hydrogen bonding by drying. In order to obtain substantially loose fibers, the hydrogen bonds must be broken. Some of the fibers are expected to remain bonded. These are called knots or knits depending on the size. Usually, only a few knots and knits are expected to remain after breaking the hydrogen bonds between the fibers.

  There are also problems associated with providing chemical wood pulp fibers at a level of 65% by weight or higher of the total weight of the fiber / polymer mixture. The lower amount of polymer means that it is more difficult to disperse the fibers in the polymer matrix. The fiber / polymer mixture becomes more viscous as the amount of fiber increases, thus making it more difficult to move and disperse the fibers within the matrix. The objective is to have almost no fiber agglomerates.

  In one embodiment, the wood pulp feed of the present invention is produced by mechanically dicing wood pulp sheet material. In one embodiment, the wood pulp feed is diced into hexagons for use with conventional feeding equipment. In other embodiments, the shape may be triangular, rectangular or pentagonal particles. The composite material of the present invention is produced by melt processing a polymer matrix with a chemical wood pulp feed. In one embodiment, the chemical wood pulp feed is uniformly dispersed in the polymer matrix after melt processing.

  The present invention is directed to a solution for providing an economical means of producing composite materials containing well dispersed chemical wood pulp fibers. This is accomplished by utilizing a wood pulp feed that has increased bulk density and can be fed to the melt processing equipment using conventional feeding techniques. The composite material of the present invention has wood pulp fibers well dispersed in a polymer matrix.

  The hydrogen bonded cellulose wood pulp fibers are then dispersed in the polymer. One method is to make a fiber-rich masterbatch having 65-85 wt% cellulose wood pulp fibers and 15-35 wt% polymer. If necessary, a part of the polymer may be a compatibilizer.

The initial addition of cellulose pulp fibers to the polymer is a two step operation.
In the first step, the pulp particles are mixed with the polymer by a mixing operation. Mixing may be carried out in a thermokinetic mixer or a Gelimat mixer.

  The amount of chemical cellulose wood pulp fibers in the material is 65-85% by weight and the amount of polymer is 15-35% by weight. If a compatibilizer is used, the amount of polymer is expected to be reduced by the amount of compatibilizer. If 5 wt% compatibilizer is used, the amount of polymer is expected to be 5 wt% less. Non-polar polymers such as olefins are expected to use compatibilizers. Typical compatibilizers are graft copolymers such as, for example, maleic anhydride polypropylene or maleic anhydride polyethylene. If the polymer is polypropylene, it is expected that up to 2% by weight of antioxidant will also be used. In one embodiment, 0.5% by weight of antioxidant is expected to be used. The fiber and polymer are expected to exit the thermokinetic mixer as a fluffy material.

  FIG. 6 shows the mixer 30. The mixer 30 has a hopper 32 through which the material is supplied. The material is conveyed by a screw feeder 34 to a mixing chamber 36 in which a blade 38 rotates rapidly by a motor 40. As the blade 38 rotates in the mixture, the centrifugal force generated by the blade 38 causes the material to move outward toward the mixing chamber wall 42. Frictional heat melts the polymeric material, polymer, and compatibilizer, and the fibers are mixed into the polymer. After mixing, the polymer is removed from the mixing chamber 36 via the door 44.

  Another method that can be used in the first step is a twin screw extruder with an open die plate. The twin screw extruder has a die plate with an open end so that the material flow from the extruder is not hindered. The amounts of fiber, polymer, and compatibilizer are the same as described above. The material is expected to exit the twin screw extruder as a massed material. The twin screw mixer and its operation are described in more detail below.

  The problem to be solved is to provide the fibers in a substantially loose form in a polymer matrix and to obtain wood pulp fibers in which the wood pulp fibers / composites are substantially uniformly dispersed throughout the composite material Thus, the fiber is weighed in a substantially constant amount and fed to the polymer. The present invention provides diced particles of chemical wood pulp taken from a wood pulp sheet, and further weighs and feeds the polymer to substantially polymerize wood pulp fibers while mixing the wood pulp and polymer. To unify.

  In other embodiments, an oil such as mineral oil may be added to the composite material component. In one embodiment, the amount of mineral oil may be 0.1-5% by weight of the total weight of materials in the composite polymer material. In one embodiment, the amount of mineral oil may be 0.1-2% of the total weight of the materials in the composite polymer material. In one embodiment, the amount of mineral oil may be 1-2% of the total weight of the material in the composite polymer material. In one embodiment, the amount of mineral oil may be 1-1.5% of the total weight of the materials in the composite polymer material. In one embodiment, the amount of mineral oil may be 1.15% of the total weight of the materials in the composite polymer material. Mineral oil is believed to increase the amount of extrusion of the composite material through an extruder that may be used for polymer formation and help disperse the fibers in the composite material.

  Mineral oil is a viscous oil having a specific gravity of 0.8 to 0.9. Mineral oil can be clear, colorless and odorless. In one embodiment, the mineral oil is a standard white mineral oil. In one embodiment, the mineral oil is Drakol 600, CAS number 8042-47-5.

  Mineral oil is added to the first masterbatch mixer and may also be added to subsequent mixers. Mineral oil is added along with pulp particles and thermoplastic polymer to facilitate material mixing and processing speed.

  In FIG. 10, bleached chemical wood pulp fiber particles 24 or 24 a are fed into a twin screw extruder 100 via a hopper 102. Furthermore, polymer pellets are also fed into the twin screw extruder 100 via the hopper 104. The hopper 104 may be in front of or after the hopper 102. Wood pulp fiber particles and polymer pellets may be fed into a twin screw extruder via the same hopper.

  In one embodiment, the twin screw extruder has an open die face. In other embodiments, the twin screw extruder has a partially open die face by using a restrictor 105. The partial opening 106 may have any shape. In one embodiment, the opening has an area of 20-80% of the area of the open die face. In other embodiments, the opening has an area of 40-60% of the total area of the open die face. Partially open die faces promote fiber dispersion in the polymer.

  FIG. 11 shows one embodiment of this die face. In this embodiment, the transition from the die face region to the opening region is gradual. The upper and lower surfaces 107 and 108 of the restrictor 105 extend inward so that the flow of material to the opening 106 is restricted, thereby providing an opening that is lower than the open die face. Provided, the side surfaces 109 and 110 extend outwardly, thereby providing a wider opening than the open die face. The restrictor withstands the pressure of the material being pushed through the extruder and may be a single machined part.

  FIG. 12 shows another embodiment. The opening is divided into several openings 111. Even in this case, in one embodiment, the opening has an area of 20-80% of the area of the open die face. In other embodiments, the opening has an area of 40-60% of the total area of the open die face.

The amount of bleached chemical wood pulp fiber added to the polymer in the twin screw extruder is 65-85% by weight of the total weight of fiber, polymer, and additive.
Embodiments of the first stage include a masterbatch composite material in which 65% to 85% by weight of the material is fiber and a diluted composite material in which 10% to 50% by weight of the material is fiber. ) And both are the same.

  The present invention is also directed to a solution for providing an economical means of producing a composite polymeric material comprising 10-50 weight percent chemical wood pulp fibers. In one embodiment, the pulp fibers are uniformly dispersed in the polymer matrix.

In one embodiment, the chemical wood pulp fibers are bleached chemical wood pulp fibers. There are reasons to use bleached chemical wood pulp fibers instead of unbleached wood pulp fibers.
One reason is color. Bleached chemical wood pulp fibers are substantially all cellulose and hemicellulose. Since cellulose and hemicellulose have no original color, it is expected that the composite material will be colored little or not at all. On the other hand, unbleached fibers such as natural fibers such as kenaf or whole wood fibers are colored in the natural state or are expected to become colored when heated to the temperature of the thermoplastic treatment and other lignins and other Has up to 50% of compound. Composite materials comprising unbleached, natural or whole wood fibers are expected to be colored, possibly dark brown.

  Another reason is odor. Because cellulose has no odor, composite materials containing bleached wood pulp fibers have little odor due to cellulose. Lignin and other components in unbleached fibers give off a strong characteristic odor when melt processed, giving the resulting composite a strong odor and its use in enclosed areas such as, for example, automotive interiors Limit.

  Embodiments relating to incompatible polymers may contain the following components:

  In the masterbatch, the material is expected to be further processed in a pellet mill, such as a California pellet mill, or in a single screw extruder, such as a Bonnot single screw extruder.

  Figures 7 and 8 show the laboratory version of the pellet mill. The pellet mill 50 has a hopper 52 into which the fiber / polymer composite 54 from a thermokinetic mixer or twin screw extruder or other mixer is transferred. The composite 54 is dropped onto a perforated plate 56. The aperture 58 on the perforated plate 56 is the size of the diameter of the extruded pellet 60. The composite material is passed through the aperture 58 by the pair of wheels 62, and the pellet 60 is formed. The wheel 62 is mounted on the shaft 64. The shaft 64 is mounted on the rotor 66. The rotor 66 is rotated by a motor (not shown) to rotate the wheel 62 around the perforated plate 56. The pellet 60 is taken out from this apparatus and collected.

  Fibers tend to agglomerate at higher fiber levels. A single screw extruder can be used to disperse the cellulose pulp fibers throughout the polymer. It has been discovered that to achieve fiber dispersion it is necessary to change the direction of material flow through the extruder. This is done by placing pins that extend from the outer wall of the extruder in the direction of the extruder gap. Extruded pellets are formed by passing material from this device through the die holes. Because the material tends to clog at the back of the die plate, the material may not be able to pass through the die efficiently. By adding a wiper to the backside of the die face, the composite passes more efficiently through the die holes.

  FIG. 9 shows a single screw extruder. The extruder 80 has a hopper 82 into which the fiber composite material from the mixer is put. The hopper 82 is connected to the barrel 84, and a screw 86 passes through the barrel 84. Screw 86 is rotated by a motor (not shown) to direct the material in the barrel toward die plate 88. The screw is designed such that when the composite material passes through the barrel, pressure is applied to some degree to the composite material. The pin 90 is disposed along the barrel. By moving the pin 90 inward or outward, the flow of material through the barrel may be altered to promote fiber distribution into the polymer. The die plate 86 has a large number of apertures 92 through which material passes to form strands, possibly cut into pellets.

  In one embodiment, the first twin screw mixer may be directly connected to the second single screw extruder and the material is expected to be passed directly from the first mixer to the second mixer. . Both of these may be operated by the same motor. FIG. 14 shows this embodiment.

The masterbatch pellets contain 65-85% by weight chemical wood pulp fibers and 15-35% by weight polymer.
FIG. 10 is an embodiment of a method and apparatus for producing a polymer composite having 50% or less chemical wood pulp fibers.

  The material from the twin screw extruder is transferred to the second twin screw extruder 120 and additional polymer is added via the hopper 122. Other ingredients may be added to the throat as well or via a side stuffer (not shown). The polymer is the same as that used in the first twin screw extruder 100. The amount of polymer added is that amount necessary to achieve the desired wood pulp fiber content in the composite.

  In batch operation, the composite is cycled twice through the first twin screw extruder, and additional polymer is added during the second pass of the extruder, thereby allowing the first twin screw extruder to move to the second twin screw extruder. It can be used as a screw extruder. In this operation, the die face of the extruder is expected to change from an open or partially open die face to a die face with a die opening to form an extrudate.

Additional additives can also be added to the second twin screw extruder.
The composite material is extruded through a die opening in the die plate and cut to a predetermined size.

  The extrudate from the second twin screw extruder may be formed into pellets by an underwater pelletizer. Since pulp fibers are hydrophilic, it has been considered that underwater pelletizers cannot be used with pulp fibers. An underwater pelletizer can be used and the water content of the fibers in the pellets was found to be 1% or less. In some embodiments, there are no deleterious effects from water uptake.

  FIG. 15 is a schematic diagram of an underwater pelletizer. The pellets exit the second twin screw extruder 120 through the die aperture 124 in the die plate 126 and are sent to the cutting chamber 128 where the extrudate is cut into pellets. The pellets are transported from the cutting chamber 128 to the separation section 130 with water by a pipe 132. Hot pellets are cooled with water. In one embodiment, the pellets are formed into spheroids during processing. In the separation section 130, the pellets are separated from the water by filtration. The separated water passes through the heat exchanger 134 where the water is cooled. The water returns to the cutting chamber 128 through the pipe 136.

  The separated pellets pass through dryer section 138 where the remaining water is removed. Although a cyclone dryer is shown, the dryer may be any type of dryer. The dried pellets then enter a pellet chute and are sent to a bagging operation where the pellets are bagged.

  There are a number of manufacturers of underwater pelletizers. Such manufacturers include Gala Industries, Neoplast, Berlyn, and Davis Standard.

Underwater pelletizers have many advantages, but any type of pelletizer can be used.
A melt pump can be used to ensure continuous and regular extrudate supply by buffering the pressure and flow oscillations generated by the twin screw extruder.

FIG. 14 shows another embodiment of the mixing system.
It may be necessary to disperse more cellulose wood pulp fibers in the polymer. A mixing device such as a single screw extruder shown in FIG. 9 is arranged between the two twin screw mixers. A single screw extruder can be used to further disperse the fibers.

  In the discussion of the various embodiments of the let-down pellets shown below, it is understood that each individual pellet may be one or more of each of these embodiments. Shall.

  In some of the following tests, the composite polymer is molded into a dogbone shape, which has the following dimensions: 6 to 3/8 inch long, 1/8 inch thick, It has a 3/4 inch wide end cross section, a 2/1 inch wide central cross section, and a 2.7 inch or 68 mm central cross section length. These are the dimensions of the dogbone when the dogbone is mentioned in the text. The dogbone is formed under heat and compression. Molding of masterbatch pellets containing a large amount of fiber causes fiber degradation due to the large amount of heat and pressure required to mold the material, thereby turning the fiber brown.

  In one embodiment, a diluted composite material having 10-50% by weight bleached chemical wood pulp fibers is provided. The rest is polymer and other additives. In another embodiment, a let-down composite having 20 to 40 weight percent bleached chemical wood pulp fibers is provided, the remainder being a polymer and other additives as described above.

  In one embodiment, the diluted composite material has a whiteness of at least 20 as measured by a whiteness test. In other embodiments, the diluted composite material has a whiteness of at least 30 as measured by a whiteness test.

  Masterbatch compositions with 65% by weight or more fibers in the composition cause the fibers to deteriorate due to the heat and pressure required to form the material into dogbone, resulting in brown or black coloration. It does not have this whiteness.

Whiteness test This method focused a single light source through the aperture at a 45 degree angle on the dogbone, passing the reflected light through a filter with standard spectral characteristics and placing it perpendicular to the top surface of the dogbone. This is a method of measuring with a photodetector. The amount of reflected light is compared to magnesium oxide having a known spectral characteristic stored in the instrument's memory. The ratio of reflected light to magnesium oxide is expressed as a percentage.

  This instrument is a Brightimeter MICRO S-5 from Technidyne. The instrument is expected to warm up 30 minutes before testing. The reflected light passes through a filter having an effective wavelength of 457 nanometers.

  One dogbone is tested at different composite conditions such as different polymers, different polymer amounts, different fiber amounts, different additives, etc. Place a 1 kg weight on top of the dogbone. The dogbone goes around the four main compass points, gets the four chromaticity values, and averages them.

  In one embodiment of the diluted composite material, the average dispersity of the bleached chemical wood pulp fibers in the diluted composite material is equal to or greater than 90%. In another embodiment of the diluted composite material, the average dispersity of the bleached chemical wood pulp fibers in the diluted composite material is equal to or greater than 95%. In other embodiments, the average dispersity of the bleached chemical wood pulp fibers in the diluted composite material is equal to or greater than 98%. In other embodiments, the average dispersity of the bleached chemical wood pulp fibers in the diluted composite material is equal to or greater than 99%. Average dispersity means that the fibers are distributed substantially uniformly throughout the composite, and the percentage is the number of fibers that are not agglomerated. These percentages are determined using a dispersion test.

Dispersion test Measurement of the degree of dispersion is accomplished by using ImageJ (NIH). ImageJ is freeware that can be downloaded at http // imagej.nih.gov / ij / download.html. Erode, Subtract Background, Analyze Particles, and other commands used in the following custom macros are standard commands in ImageJ. Macros can obtain information simply by using standard IMageJ commands in a predetermined order.

  The sample is a dogbone as described above. Take a sample X-ray and scan it into a digital image. Open the image in ImageJ and analyze the image using a custom macro.

  Custom macros locate the sample in the image. The custom macro then executes the erosion command four times to remove sample boundary artifacts. Apply a Subtract Background command with a 5 pixel diameter rolling ball, bright background, and smoothing disabled. Convert a grayscale image to black and white by using a user specified threshold. A typical threshold is 241.

  The image here shows black particles corresponding to undispersed fibers. Count particles using the Analyze Particles command. Count all particles except those that touch the edge. This is because the edge effect that appears macroscopically but is not actually a particle often occurs.

  Another hypothesis is that the diced wood pulp material fed to the process is expected to split or delaminate along the centerline, and these split particles further split or delaminate along the centerline. There is a possibility of delamination. The macro assumes that half of the analyzed particles have been split or delaminated once and the other half have been split or delaminated twice.

  The macro reports the area of undispersed particles. The macro assumes that half of the total area is occupied by undispersed particles that have been split once and half of the total area is occupied by particles that have been split twice.

The total weight of undispersed particles or fibers is then calculated. In the discussion below, a pulp sheet having a basis weight of 750 grams / square meter (gsm) is used. Macro estimates that half the basis weight of the particle is a single split particle, has a basis weight of 375 gsm, and the other half of the analyzed particle is a double split particle, having a basis weight of 187 gsm To do. The total weight of undispersed particles or fibers is given by the following formula:
Weight of undispersed particles = 0.0001 × [0.5 × (area of undispersed particles) cm ² × (375 gsm) + 0.5 × (area of undispersed particles) cm ² × (187 gsm)]
Determined by.

The weight percent of undispersed particles is calculated using the following formula:
Calculated by weight% of undispersed particles = 100 × weight of undispersed particles / total weight of fibers in sample.

The weight percent of dispersed fibers is calculated by subtracting the weight percent of undispersed particles from 100 percent.
The actual macro is as follows.

  The degree of dispersion may depend on the fiber content. In one embodiment of a composite material having 20 wt% bleached chemical wood pulp fibers, the degree of dispersion was found to be equal to or greater than 99%. In one embodiment of a composite material having 30% by weight bleached chemical wood pulp fibers, the degree of dispersion was found to be equal to or greater than 98%. In one embodiment of a composite material having 40 wt% bleached chemical wood pulp fibers, the degree of dispersion was found to be equal to or greater than 92%.

  The odor level of the diluted composite was compared to the odor level of the thermoplastic polymer containing other materials. Contains three levels of dilute composites: a polymer containing 20% by weight bleached chemical wood pulp fibers, a polymer containing 30% by weight bleached chemical wood pulp fibers, and 40% by weight bleached chemical wood pulp fibers The polymer was tested. These were compared to a thermoplastic polymer alone control, a polymer containing 30% glass fiber, a polymer containing 30% sisal, and a polymer containing 30% maple wood flour.

  The test used was ASTM E679, using an Ac'scent olfactometer available from St. Croix Sensory, 1-800-879-9231. In this test, samples are placed in a 9 L Tedlar bag at 40 ° C. for 24 hours prior to testing. The olfactory meter uses a venture valve system that draws air from the sample bag by a fast flow of odorless air through the valve and sends it to the air stream. A dilution factor of 8-66,000 can be obtained. The reported number is the dilution factor at which sample odor was detected. The higher the dilution number, the stronger the odor of the material. The results are as follows.

  The dilution level of the thermoplastic polymer containing bleached chemical wood pulp fibers is lower than any other material such as glass fiber and is substantially the same regardless of the amount of wood pulp fibers incorporated into the thermoplastic polymer I understand.

  In order to determine the usefulness of the diluted composite material, a Moldflow® report of diluted pellets was requested. Moldflow® reports are used in the industry to determine how much material is circulated through the molding process and to gain insight into the behavior of the material during the injection molding process. In this report, a polypropylene composite containing 30% bleached chemical wood pulp fibers was compared to two 20% glass filled polypropylene composites.

  The table from the report below provides a study of the cooling time for a sturdy part. A runner is a channel leading to a mold, and this mold may be a hot runner or a cold runner. In the case of cold, the part must be used to remove the runner, trim the edges, reuse it, or throw it away as waste. If hot, keep the contents molten and use this as the first bit of injected plastic for the next injection cycle.

  It can be seen that the bleached chemical wood pulp fiber filled polypropylene had a much shorter cooling time than the glass filled polypropylene. This translates to faster cycle times and more parts being produced in a given period.

  This is also shown in another table from the report, a table comparing the typical “average” cycle times of molded parts for 20% glass filled polypropylene material and 30% bleached chemical wood pulp fiber filled polypropylene material. It is.

A typical “average” cycle time for materials filled with chemical wood pulp fibers is 75% of the cycle time for glass-filled materials. This results in a much faster production rate.
It is also noted that compositions comprising 10-50% by weight wood pulp fibers and 25-85% by weight thermoplastic polymer have other properties. The ends of the molded structure are free or substantially free of tactile scratches. A tactile wound is a wound that can be felt when a hand or finger is moved along the edge of a molded part. Tactile wounds should be distinguished from visual wounds. The part may have a visual edge scar that is visible but may not have a tactile edge scar that can be felt. The end of the part is the boundary layer between the two faces of the part. The end of the part is usually rounded or at a predetermined angle with the face of the part. The end of the part is often rounded or at an angle of 90 ° with the face of the part. In one embodiment, the end is expected to be free of tactile flaws. In other embodiments, the ends are expected to have an average of one or less tactile wounds per foot or less of the end. In other embodiments, the ends are expected to have an average of 2 or less tactile scratches per foot or less of the end. The term “1 foot or less” means that if the total edge length is less than the exact number of feet, the total edge length is treated as the second largest foot length in determining tactile flaws. means. For example, if the structure has a total edge length of 8 inches, the total edge length is treated as having a total edge length of 1 foot when determining the number of tactile scratches, and the total edge length Is 2 feet 4 inches, the total edge length is treated as having a total edge length of 3 feet when determining the number of tactile scratches.

  Masterbatch pellets containing 65-85 weight percent fibers are also let down to 10-50 weight percent fibers or 20-40 weight percent fibers in an injection molding operation to form a molded part. )be able to. The pellets are added to the injection molding machine, and the additional thermoplastic polymer necessary to reduce the amount of fibers to 10-50 weight percent fibers or 20-40 weight percent fibers is added to the injection molding machine. The polymer is let down to the final fiber volume and at the same time a molded part is formed. This reduces the cost of reducing the amount of fiber as a separate operation.

  While exemplary embodiments have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the claimed subject matter.

10 Particles 12, 14, 16, 18, 20, 22 Side 24 Upper part of particle 26 Lower part of particle 30 Mixer 32 Hopper 34 Screw feeder 36 Mixing chamber 38 Blade 40 Motor 42 Mixing chamber wall 44 Door 50 Pellet mill 52 Hopper 54 Fiber / Polymer composite 56 Perforated plate 58 Aperture 60 Pellet 62 Wheel 64 Shaft 66 Rotor 80 Extruder 82 Hopper 84 Barrel 86 Screw 88 Die plate 90 Pin 92 Aperture 100 First twin screw extruder 102, 104 Hopper 105 restrictor 106 Opening 107 Upper surface of restrictor 108 Lower surface of restrictor 109, 110 Side surface 120 Second twin screw extruder 122 Hopper

Claims (16)

A method for producing pellets comprising wood pulp fibers and a thermoplastic polymer, the method comprising:
Extruding an extrudate comprising 10-50 wt% wood pulp fibers and 45-85 wt% thermoplastic polymer with a die;
Cutting the extrudate into pellets,
Removing the pellets from the extrudate using water at a lower temperature than the extrudate,
Filtering the pellets from the water,
Here, the wood pulp fibers in the pellets have a water content of 1% or less.   The method of claim 1, wherein the wood pulp fibers are bleached chemical wood pulp fibers.   The thermoplastic polymer is a biopolymer, polylactic acid, cellulose acetate, cellulose propionate, cellulose butyrate, polycarbonate, polyethylene terephthalate, polyolefin, polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polystyrene, The method of claim 1, selected from the group consisting of polystyrene copolymers, acrylonitrile-butadiene-styrene copolymers, styrene block copolymers, vinyl chloride, and recycled plastics. Cooling the filtered water from the pellets;
The method of claim 1, further comprising recycling water to the extrudate.   The method of claim 4, wherein the wood pulp fibers are bleached chemical wood pulp fibers.   The thermoplastic polymer is a biopolymer, polylactic acid, cellulose acetate, cellulose propionate, cellulose butyrate, polycarbonate, polyethylene terephthalate, polyolefin, polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polystyrene, 5. The method of claim 4, selected from the group consisting of polystyrene copolymers, acrylonitrile-butadiene-styrene copolymers, styrene block copolymers, vinyl chloride, and recycled plastics.   The method of claim 1, further comprising pumping the material to a die.   The process of claim 1 wherein the extrudate comprises 20-40% by weight wood pulp fibers and 55- & 5% by weight thermoplastic polymer.   The method of claim 1, wherein the wood pulp fibers are not swollen.   The method of claim 9, wherein the wood pulp fibers are bleached chemical wood pulp fibers.   The thermoplastic polymer is a biopolymer, polylactic acid, cellulose acetate, cellulose propionate, cellulose butyrate, polycarbonate, polyethylene terephthalate, polyolefin, polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polystyrene, 10. The method of claim 9, selected from the group consisting of polystyrene copolymers, acrylonitrile-butadiene-styrene copolymers, styrene block copolymers, vinyl chloride, and recycled plastics. Cooling the filtered water from the pellets;
The method of claim 9, further comprising recycling water to the extrudate.   The method of claim 12, wherein the wood pulp fibers are bleached chemical wood pulp fibers.   The thermoplastic polymer is a biopolymer, polylactic acid, cellulose acetate, cellulose propionate, cellulose butyrate, polycarbonate, polyethylene terephthalate, polyolefin, polyethylene, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, polystyrene, 13. The method of claim 12, wherein the method is selected from the group consisting of polystyrene copolymers, acrylonitrile-butadiene-styrene copolymers, styrene block copolymers, vinyl chloride, and recycled plastics.   The method of claim 9, further comprising pumping the material to a die.   10. The method of claim 9, wherein the extrudate comprises 20-40% by weight wood pulp fibers and 55- & 5% by weight thermoplastic polymer.

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